It has been known in the field of communications networks to configure network nodes as restricted transit nodes. Namely, it has been known to restrict the transit of network traffic through specified nodes of a network so as to inhibit such traffic, or connections related thereto, from traversing one or more network nodes. Typically, the provisioning of restricted transit status in respect of a network node may prohibit network traffic or connections from transiting through the node, but may permit traffic or connections to originate or terminate at such a node. In known restricted transit mechanisms, during such time that a network node has been designated as a restricted transit node, no traffic is ordinarily permitted to transit the node. On the other hand, while a network node is not designated as a restricted transit node, all traffic is ordinarily permitted to transit the node.
In contrast to restricted transit routing, policy routing is utilized in the art of communications networks in order to control the manner in which network traffic or its related network connections are routed across a routing domain of the network. One known routing and signaling specification for the support of policy routing is that provided by the specification of The ATM Forum Technical Committee entitled “Policy Routing”, version 1.0, which is dated April 2003 and is identified as document number af-cs-0195.000 (the “Policy Routing Specification”), the contents of which are hereby incorporated by reference. The Policy Routing Specification is an addendum to existing signaling specifications of The ATM Forum Technical Committee, namely: “ATM User-Network Interface (UNI) Signaling Specification”, version 4.1, which is dated April 2002 and is identified as document number af-sig-0061.002; “ATM Inter-Network Interface Specification”, version 1.1, which is dated September 2002 and is identified as document number af-cs-0125.002; and “Private Network-Network Interface Specification, version 1.1, which is dated April 2002 and is identified as document number af-pnni-0055.002, all as known to those skilled in the art of communications networks.
In typical policy routing mechanisms, and as described in the Policy Routing Specification, Network Elements (“Ne”) or Resource Partitions (“Rp”) may be identified and advertised throughout the network topology for purposes of routing traffic through the network in question. For instance, a network element may be a link or the entirety of a trunk group, whereas a resource partition may be a bandwidth partition of such a trunk group. In forwarding a traffic stream, a policy based request for forwarding may be made, wherein the request may describe a forwarding constraint to either (i) prescribe the avoidance or requirement of one or more particular network elements or (ii) prescribe the requirement of one or more particular resource partitions. Such a policy based request may be communicated by way of the forwarding constraint, such as a policy constraint, being assigned to a connection and signaled during the establishment of same. A node which is initiating the establishment of the network path for a traffic stream will use the advertised network elements and resource partitions together with the signaled policy constraint to compute or otherwise establish a network path that satisfies the constraint in question.
Policy routing capabilities may be used in communications networks to provide varying services based on different network utilization strategies. For instance, policy routing may be deployed in the provisioning of Virtual Backbone Networks (“VBN”), in the selection or avoidance of network paths associated with a predetermined link quality, in the routing of connections utilizing multiple ordered policy constraints, in the specification and use of bare network resources for inter-network core networks, in bandwidth partitioning between SVC and SPVC connections, and in the dynamic allocation of network bandwidth among identifiable categories of connections. However, it has not been known to utilize policy routing in conjunction with restricted transit capability so that the latter can be enabled or disabled in predetermined instances based on a specified policy.